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CBSE Class 10 Science Board Question Paper 2022 (Term-II) with Solutions
Time Allowed: 2 hours
Maximum Marks: 40
General Instructions
- This question paper contains 15 questions. All questions are compulsory.
- This question paper is divided into three Sections viz. Section A, B and C.
- Section A – Question numbers 1 to 7 are short answer type questions. Each question carries two marks.
- Section B – Question numbers 8 to 13 are also short answer type questions. Each question carries three marks.
- Section C – Question numbers 14 to 15 are case based questions. Each question carries four marks.
- Internal choices have been provided in some questions. Only one of the alternatives has to be attempted.
- Question 1 and Question 8 and Question 14 have replaced.
Section – A
Question 1.
When hydrogen gas is passed over heated copper (II) oxide, copper and steam are formed. Write the balanced chemical equation for this reaction and state (i) the substance oxidized and (ii) the substance reduced in the reaction.
Answer:
(i) Substance oxidized = H
2
(Hydrogen gas)
(ii) Substance reduced = CuO (Copper oxide)
Question 2.
As shown in the diagram an aluminium rod ‘AB’ is suspended horizontally between the two poles of a strong horse-shoe magnet in such a way that the axis of rod is horizontal and the direction of the magnetic field is vertically upward. The rod is connected in series with a battery and a key.
State giving reason:
(i) What is observed when a current is passed through the aluminum rod form end B to end A?
(ii) What change is observed in a situation in which the axis of the rod ‘AB’ is moved and aligned parallel to the magnetic field and current is passed in the rod in the same direction?
OR
“Magnetic field is a physical quantity that has both direction and magnitude.” How can this statement be proved with the help of magnetic field lines of a bar magnet?
Answer:
(a) The rod moves in the inward direction of the magnet and this direction of motion is perpendicular to the magnetic field direction of the magnet.
(b) No motion of the rod will be observed in such a case as the value of force on the current carrying rod becomes zero when current direction is parallel to the magnetic field direction.
Or, When a magnetic compass is brought near any point of a magnetic field line of a bar magnet then the north pole of the compass is directed towards ‘S’ pole of the Bar magnet. The number of magnetic field lines are closely packed near the poles of the bar magnet and the gap between them goes on increasing as we move away from the magnet thus showing decrease in the magnitude of magnetic field.
Question 3.
Using height (tallness/dwarfness) of a plant as an example, show that genes control the characteristics or traits in an organism.
OR
In a cross between red coloured and white coloured flowers, when plants with red coloured flowers of F1 generation were self pollinated, plants of F2 generation were obtained in which 75% of plants were with red flowers and 25% plants were with white flowers. Explain the inheritance of traits in the above cross with the help of a flow chart only along with the ratio of plants obtained.
Answer:
When a plant pure tall (having genes of Tallness from both parents) is crossed with a dwarf plant (having genes of dwarfness from both parents), then offspring plant is Tall plant having genes of Tallness from one parent and gene of dwarfness from the other parent thus showing gene of Tallness is dominant over the gene of dwarfness.
Thus this shows that genes control the characteristics or traits in an organism.
Question 4.
Mention the functions of (a) Placenta (b) Fallopian tubes (c) uterus (d) Ovary in the human reproductive system.
Answer:
(a) Placenta: The embryo gets nutrition from the mother’s blood with the help of it. Waste substances from the embryo are also transferred into the mother’s blood through the placenta.
(b) Fallopian Tube : It is the site of fertilization of egg by the male sperm.
(c) Uterus : It is a muscular sac like structure where the development of the embryo and foetus into child takes place.
(d) Ovary : It produces the ovum or egg cell i.e., female gamete. It also produces two hormones which control changes in the body of female during puberty and Pregnancy.
Question 5.
” The improvement in our lifestyle has led to the generation of large amount of waste material.” List two reasons to justify this statement.
OR
“The change in packaging has resulted in waste becoming non-biodegradable.”
Giving two examples from daily life, justify this statement.
Answer:
Now a days, man is using large number of electric and electronic devices. When these devices become old or out of fashion, these are disposed of as wastes.
In our new lifestyle, man is increasingly using cars and bikes etc., as personal mode of transport. Disposal of such older vehicles also generates large amount of waste materials. Thus we can say “The improvement in our lifestyle has led to the generation of large amount of waste materials.”
OR
Now a days, we use Polythene bags as carry bags instead of Paper bags. Polythene bags when are thrown as waste. These are non-biodegradable wastes. We use thermocol also as packaging material; that too in the waste form is a non- biodegradable waste.
So we can say,” The Change in packaging has resulted in waste becoming non-biodegradable.”
Question 6.
(a) Differentiate between binary fission in Amoeba and binary fission in Leishmania.
(b) How does reproduction take place in malarial parasite?
Answer:
(a) In Amoeba, the splitting of two cells can take place in any plane during the cell division. While in Leishmania, splitting of two cells takes place in a definite orientation during the cell division.
(b) In Malarial Parasite (Plasmodium) reproduction takes place by Multiple Fission.
Question 7.
Consider the carbon compounds having following molecular formula :
(i) C
3
H
6
(ii) C
3
H
8
(iii) C
4
H
6
(iv) C
6
H
6
(v) C
6
H
12
(a) State the number of double covalent bonds present in C
3
H
6
.
(b) Write the formula of first member of the homologous series to which the carbon compound C
4
H
6
belongs.
(c) Which one of the above compounds forms ring structure of carbon atoms?
(d) Identify, which of the above compounds, is a member of alkane series.
Answer:
(a) Only one double covalent bond is present in C
3
H
6
.
(b) C
2
H
2
(Ethyne)
(c) C
6
H
6
(Benzene) forms ring structure of carbon atoms.
(d) C
3
H
8
(Propane) is a member of alkane series.
Section – B
Question 8.
State reason for the following:
(i) dry HCl gas does not change the colour of the dry blue litmus paper.
(ii) alcohol and glucose also contain hydrogen, but do not conduct electricity.
(iii) Cone, of H
3
0
+
ion is affected when a solution of an acid is diluted.
Answer:
(i) Dry HCl gas does not contain any hydrogen ions in it, so it does not show acidic behaviour. Dry HCl gas does not change the colour of dry blue litmus paper because b it has no hydrogen ions [H
+
(aq)] in it. However, when HCl gas dissolves in water, it forms hydrogen ions and hence shows acidic behaviour.
(ii) The aqueous solutions of glucose and alcohol do not show acidic character because their hydrogen does not separate out as hydrogen ions [H + (aq) ions] on dissolving in water. Hence, they do not conduct electricity.
(iii) • An acid is a substance which dissociates on dissolving in water to produce hydrogen ions [H
+
(aq) ions].
• Hydrogen ions do not exist as H
+
ions in a solution, they attach themselves to the polar water molecules to form hydronium ions, H
3
O
+
.
H
+
+ H
2
O → H
3
O
+
• When a solution of an acid is diluted, the number of [H
3
O
+
] ions per unit volume decreases. Thus pH of the solution increases.
Question 9.
What are trophic levels? Why are autotrophs considered to be at the first trophic level of all food chains? State the reason for limited number of trophic levels in nature.
Answer:
Each step in the food chain is known as a Trophic Level. As green plants (autotrophs) make their own food by the process of photosynthesis. This food is then transferred to the subsequent levels of a food chain. So autotrophs are considered to be at the first trophic level.
Each food chain has limited number of trophic levels as the flow of energy of food through them follows the Ten percent law of flow of energy. So availability of food energy becomes very less after a few trophic levels of a food chain.
Question 10.
In flowering plants the pollen grains are transferred to stigma by pollination but the female germ cells are present in the ovary. Explain with the help of a labelled diagram (only concerned parts), how the male germ cell reaches the ovary.
Answer:
The transfer of pollen grains from anthers (male sexual parts) of a flower to the stigma part of the pistil (female sexual part) is known as pollination. Pollination is done by insects, birds, wind and water.
Pollination can occur in two ways:
(i) Self pollination. When the pollen grains from the anther of a flower are transferred to the stigma of the same flower or another flower on the same plant, it is called self pollination.
(ii) Cross pollination. When the pollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant, it is called cross pollination.
When a pollen grain falls on the stigma of the carpel, it grows a pollen tube downwards through the style towards the female gamete in the ovary. A male gamete moves down the tube. When the pollen tube enters the ovule, its tip bursts open and male gamete comes out of the pollen tube and combines with the nucleus of the female gamete and forms zygote. This process is known as fertilization.
Question 11.
“Two different forms of carbon – diamond and graphite have different structures and very different physical properties even though their chemical properties are same.” Explain why.
OR
State the reasons, why Carbon cannot
(i) Lose four electrons to form C
4+
cation, and
(ii) Gain four electrons to form C
4-
anion.
How does Carbon overcome this problem to from compounds?
Answer:
Both Diamond and Graphite are two different forms of carbon. These show different physical properties. But as these two are forms of the Carbon element, so both show same chemical properties of carbon element.
OR
Carbon atoms have 4 electrons in their outermost shell. So needs to gain or lose electrons to attain noble gas configuration.
(i) It could lose four electrons forming C
4+
cation. But it would require a large amount of energy to remove four electrons from its outermost shell.
(ii) It could gain four electrons forming C
4-
anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
Because of these reasons, Carbon shares its valence electrons to complete its octet with other atoms to form covalent bonds.
(a) Covalent compounds are bad conductors of electricity because they do not contain ions.
(b) Covalent compounds have usually low melting and boiling points because they are made up of electronically neutral molecules. So the force of attraction between the molecules of a covalent compound is very weak. Only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting and boiling points.
Question 12.
(a) A student wants to use an electric heater, an electric bulb and an electric fan simultaneously. How should these gadgets be connected with the mains? Justify your answer giving three reasons.
(b) What is an electric fuse? How is it connected in a circuit?
Answer:
These gadgets must be connected in
(a) Parallel with the mains. By this type of Parallel combination, each gadget will get current according to its own resistance. Moreover if any of the gadgets gets damaged the other gadgets will go on working normally.
(b) Fuse : It is a safety device in the electric circuits. A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. Fiise is connected in series with the live wire in a circuit.
Question 13.
An electric motor rated 1100 W is connected to 220 V mains. Find :
(i) The current drawn from the mains.
(ii) Electric energy consumed if the motor is used for 5 hours daily for 6 days.
(iii) Total cost of energy consumed if the rate of one unit is ₹5.
OR
Study the following circuit and find :
(i) Effective resistance of the circuit.
(ii) Current drawn from the battery.
(iii) Potential difference across the 5Ω resistor.
Answer:
Given. P = 1100 W and V = 220 V
(i) I = ?
As we know, P = VI or I = \(\frac { P }{ V }\)
∴ I = \(\frac { 1100 }{ 220 }\) = 5 A
So, current of 5 Ampere is drawn.
(ii) Given. P = 1100 watt or 1.1 KW
t = 5 Hours,
days = 6 days, so total time (t) = 5 × 6 Hrs.
E = ?
As we know, E = P × t
∴ E = 1.1 × 5 × 6 = 33 kwh (kilo watt hour)
(iii) Total cost = 33 × ₹5
= ₹165 (One hundred and sixty five only)
Or
(i) Effective, R = ?
As we know, \(\frac { 1 }{ R’ }\) = \(\frac{1}{\mathrm{R}_2}\) + \(\frac{1}{\mathrm{R}_3+\mathrm{R}_4}\)
\(\frac { 1 }{ R’ }\) = \(\frac { 1 }{ 10 }\) + \(\frac{1}{6+4}\) = \(\frac { 1 }{ 10 }\) + \(\frac { 1 }{ 10 }\) = \(\frac { 2 }{ 10 }\)
R’ = 5 Ω
Now, Total R = R
1
+ R’ + R
5
= 5 + 5 + 10 = 20 Ω
(ii) I = ? and V = 20 Volt
I= \(\frac { V }{ R }\) = \(\frac { 20 }{ 20 }\) = ⇒ 1A
Current drawn = 1 Ampere (one A)
(iii) V of 5 Ω resistor = ?
I = 1A
V = I × R
∴ V (Potential difference) = 1 × 5 = 5 Volt
Section – C
This section has 02 case based questions (14 and 15).
Each case is followed by 03 sub-questions (a, b and c).
Part (a) and (b) are compulsory. However an internal choice has been provided in Part (c)
Question 14.
Study the following current-time graphs from two different sources:
(a) Name the type of current in the two cases.
(b) Use above graphs to list two differences between the current in the two cases.
(c) Identify one source each for these currents.
OR
What is meant by the statement that “the frequency of current in India is 50 Hz”?
Answer:
(I) (D.C.) – Direct Current; (II) (A.C.) – Alternating Current
(b)
| I | II |
| (I) shows Direct Current (D.C.). | (II) shows Alternating Current (A.C.). |
| The Current (I) flows in one direction only. It is called a direct current. The magnitude and direction of flow of current remains the same. | The current (II) reverses direction after equal intervals of time. It is called alternating current. The magnitude and direction of current change continuously at definite intervals of time. |
| The magnitude of current in (I) does not become zero with the passage of time. | The magnitude of (II) becomes zero after a regular time interval. |
(c) Source of D.C. → a cell, battery, solar cell, D.C. Generator
Source of A.C. → A.C. Generator.
Or, ‘The frequency of current in India is 50 Hz’ means the direction of current in India changes 100 times in 1 second as current direction changes twice in one cycle.
Question 15.
Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environment cues, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However, in human beings, the sex of an individual is largely determined genetically.
(a) In what way are the sex chromosomes ‘X’ and ‘Y different in size?
Name the mismatched pair of sex chromosome in humans.
(b) Write the number of pair/ pairs of sex chromosomes present in human beings. In which one of the parent (male/female) perfect pair/pairs of sex chromosomes are present?
(c) Citing two examples, justify the statement “Sex of an individual is not always determined genetically”.
OR
Draw a flow chart to show that sex is determined genetically in human beings.
Answer:
(a) ‘X’ chromosome is bigger in size as compared to the size of ‘Y’ chromosome. Mismatched pair of sex chromosome is XY and it is present in the male human being.
(b) One pair of sex chromosomes is present in male human beings and one pair of sex chromosomes is present in female human beings.
In the female parent, perfect pair of chromosomes is present. It is known as ‘X’ ‘X’ pair of sex chromosome.
(c) Sex in some of the animals like tortoises, turtles and snails is not determined genetically but by the environmental factors, like at which temperature the fertilized egg is kept for the development of the embryo.
Or
Sex determination flow chart:
(i) A male has one X-chromosome and one Y-chromosome. Thus half the male gametes have X-chromosomes and the other half have Y-chromosomes.
(ii) A female has two X-chromosomes. Thus all female gametes have only X-chromosomes.
(iii) If a sperm carrying Y-chromosome fertilises an ovum carrying X-chromosome, then the child born will be a boy.
(iv) If a sperm carrying X-chromosome fertilises an ovum carrying X-chromosome, then the child born will be a girl.
Therefore it is the sperm from the father that determines the sex of the child.